Many circuits, including BiCMOS integrated circuits, must pass clocks, logic control and status signals between circuits operating at different voltage values of logic levels. These circuits are commonly called logic shifters. When two circuits operating in different logic voltage domains share a common voltage rail, e.g. a common ground or return voltage rail, it is relatively easy to provide a high-speed, low-power level shifter between them.
However, this problem becomes significantly more difficult when each of the circuits has a pair of voltage rails, and none of these rails is shared with the other circuit. When voltage levels of one pair of voltage rails moves with respect to a voltage level of the other pair, the logic level at the output of the level shifter may change with respect to the logic level at its input. In a conventional high-speed level shifter, a high power is consumed in a steady mode to hold the logic level constant. Therefore, it would be desirable to provide a high-speed, low-power level shifter for supporting operations of a system having at least two pairs of power supply rails.